Handlebar tube frames for winter tubes made of polyethylene cell plastics.
The insulating keeps your hands warmer in cold weather.
I have used them now for 5 rides and enjoyed warm hands.
You also need some 6 mm polyethylene sheet, 4 pieces 3 mm x 18 mm screws & nuts and a bit contact glue to complete your tubes.
Printing and building guidance ( see pictures):
You need some skill to put this together. There are some useful hints in the pictures.
The plastics is hold in place on the frame tube with rings ( see picture) that lock in to ends.
You need to cut the cell plastic sheet on right size (115 x 91 mm) and glue it to form a ring before installing other parts.
You need 1 holkki3.stl and two of the others for one tube.
There is a removable stand in holkki3.stl that you must remove after printing.
Be careful not tightening too much just that they keep in place.